Lubricant composition containing a metal compound



United States Patent 3,236,773 LUBRICANT COMPOSITION CONTAINING A METAL COMPOUND John R. Sternniski and Stanley D. Koch, Swampscott, and

Glenn R. Wilson, Cambridge, Mass., assignors to Monsanto Research Corporation, St. Louis, Mo., a corporation of Delaware N0 Drawing. Filed May 8, 1963, Ser. No. 279,018

18 Claims. (Cl. 252-421) This invention relates to liquid fluids of high thermal stability, and more particularly, provides functional fluids comprising high temperature base fluids and certain bis(oformimidoylphenolato) metal (II) compounds as additives therefor.

Base fluids employed in functional fluid applications which are of natural occurrence, such as fats and oils, possess limited stability at elevated temperatures, above about 400 F. The demand for base fluids with improved stability at such temperatures has resulted in development of synthetic high temperature base fluids. These have generally been oxygenated carbonaceous materials, consisting of carbon, hydrogen and oxygen, such as esters and ethers.

Polyphenyl ethers have been found to be particularly useful functional fluids owing to their very good thermal stability, lubricity, and resistance to foam. For example, they are valuable as hydraulic fluids, as heat-exchange media, as atomic reactor coolants, as diffusion pump fluids, as lubricants in motor operation generally, and particularly as jet engine lubricants.

As is known in the art, petroleum lubricants, in addition to the petroleum base stock, generally include additives which impart specific desired properties to the base stock, such as rust inhibitors, anti-oxidants, extreme pressure resisting agents, lubricity improvers, detersives and the like. The additives proposed heretofore have been designed to provide petroleum base compositions for lubrication in conventional equipment such as internal combustion engines of the automotive type, diesel engines and the like, in which the temperature of use is not excessive, not exceeding about 400 F. Advanced designs such as jet aircraft design have called for effective lubrication at higher temperatures, such as 500 F. and above, and for these designs, it was found that neither the petroleum base stock nor the conventional additives used therewith were practical. The temperatures of operation exceeded the boiling point of some lubricant composition components, and generally were in a range at which both lubricant and additives were thermally unstable and decomposed.

Development of synthetic bas'e stocks like the polyphcnyl ethers having provided lubricant fluids stable at temperatures above the useful range of the mineral oils, there is now a demand for compositions in which such functional fluids, with thermal stability superior to that of the mineral oils, are compounded with additives enhancing desirable properties thereof. Many materials known as useful mineral oil additives are, as stated, excluded from utility in this connection by volatility and lack of thermal stability at the temperatures of use of the polyphenyl ethers. Furthermore, it has been found that additives conventional in mineral oil lubricants do not perform predictably upon combination with synthetic base stocks. There are significant differences in chemical structure of the stocks which can affect the response to additives: for example, whereas the mineral oils consist of aliphatic hydrocarbons, the polyphenyl ethers are, by contrast, aromatic ethers. Indeed, base stocks chemically different from the mineral oils may actually suffer chemical attack by certain additives, with deleterious effects on their superior high temperature properties Temper- 3,236,773 Patented Feb. 22, 1966 ature of operation can also affect the performance of additives, and so forth. Thus an empirical approach has been required for the provision of improved lubricants including the synthetic high temperature base stocks.

Antioxidants are among the kinds of additives desired for high temperature fluids such as the polyphenyl ether base fluids. Although the polyphenyl ethers possess extremely good thermal stability, nevertheless, at temperatures of, say, over 550 F., they tend to deteriorate, not because of a decomposition reaction, but because at the higher temperatures they become quite readily oxidizable.

The lubricity of the polyphenyl ethers is thereby impaired, since the oxidation products do not possess lubricating properties; moreover, the change in viscosity which is a consequence of the oxidation not only makes for inefli ciency, but also may clog up the moving parts of the mechanism which the lubricant was originally intended to protect. Hence, when the polyphenyl ethers are to be used at the higher temperatures under conditions requiring exposure to air, it is necessary to inhibit oxidation phenomena which the higher temperatures favor.

An object of the present invention is the provision of improved high temperature functional fluid compositions.

A particular object of the present invention is to provide polyphenyl ether base compositions having improved oxidation resistance.

These and other objects will become evident upon consideration of the following specification and claims.

It has now been found that compositions comprising a high temperature, oxygenated carbonaceous base fluid and an additive amount of a bis(o-formimid-oylphenolato) metal (II) compound of the formula (Nona HO=N- R1 R zN=CH where M is a divalent, tetracoordinating metal cation, n and m are integers of from 0 to 2, and R and R are organic substituents selected from the class consisting of aliphatic saturated hydrocarbon and aromatic radicals, have unusual ability to lubricate under oxidizing conditions at high temperatures.

The improvement in oxidation stability characteristics achieved by addition of a compound of the stated kind to the stated base fluids is unusual and surprising. The increase in viscosity exhibited by the base fluid under the same conditions can be practically eliminated. Moreover, the lubricity properties are not adversely affected by oxidation.

To provide the lubricant compositions of this invention, the metal compounds of the nature stated above are combined with a high temperature, oxygenated carbonaceous lubricant base fluid. This will be a base fluid of lubricating viscosity having a chemical structure made up of C, H and O, and characterized by thermal stability at temperatures up to at least about 500 F. In general, the lubricant compositions of this invention will be designed for lubrication of the moving parts of mechanisms operating in temperature ranges of 400 F. to 700 F; A particularly advantageous base fluid for use under these conditions comprises the above-mentioned polyphenyl ethers.

The polyphenyl ethers employed in the compositions of this invention have from 3 to 7 benzene rings and from 1 to 6 oxygen atoms, with the stated oxygen atoms joining the benzene rings in chains as ether linkages. One or more of the benzene rings in these polyphenyl ethers may be hydrocarbyl substituted. The hydrocarbyl substituents, for thermal stability, must be free of CH and aliphatic CH, so that preferred aliphatic substituents are lower saturated hydrocarbon radicals (l to 6 carbon atoms) like methyl and tert-butyl, and preferred aromatic substituents are aryl radicals like phenyl, tolyl, t-butylphenyl and a-cumyl. In the latter case, a benzene ring supplied in the hydrocarbyl substituent contributes to the total number of benzene rings in the molecule. Polyphenyl ethers consisting exclusively of chains of from 3 to 7 benzene rings with at least one oxygen atom joining the stated benzene rings in the chains as an ether linkage have particularly desirable thermal stability.

Exemplary of the polyphenyl ethers containing aliphatic carbon which are suitable for high temperature base fluids are 3-ring polyphenyl ethers like 1-(p-methylphenoxy)-4- phenoxybenzene and 2,4-diphenoxy-l-methylbenzene, 4 ring polyphenyl ethers like bis[p-(methylphenoxy)phenyl] ether and bis[p-(p-tertbutylphenoxy)phenyl]ether, and so forth.

Polyphenyl ethers consisting exclusively of benzene rings and including ether oxygen atoms linking said rings are exemplified by the triphenoxy benzenes and aryl-substituted polyphenyl ethers such as biphenylyl phenoxyphenyl ether, bi-phenylyloxyphenyl phenoxyphenyl ether, dibiphenylyl ether, dibiphenylyloxybenzene, bis(biphenylyloxyphenyl)ether, and the like.

A preferred class of the polyphenyl ethers are those consisting of benzene rings joined in a chain by oxygen atoms as ether linkages between each ring, of the formula C H O(C H O) C H where n is an integer of from 1 to 5.

Examples of the polyphenyl ethers contemplated in this class are the bis(phenoxyphenyl)ethers (4 benzene rings joined in a chain by 3 oxygen atoms), illustrative of which is bis(m-phenoxyphenyl)ether. The bis(phenoxyphenoxy)benzenes are particularly valuable in the present connection. Illustrative of these are m-bis(mphenoxyphenoxy)benzene, m-bis (p-phenoxyphenoxy)benzene, o-bis(o-phenoxyphenoxy)benzene, and so forth. Further, the polyphenyl ethers contemplated herein include the bis(phenoxyphenoxyphenyl)ethers such as his- [m- (m-phenoxyphenoxy) phenyl ether, bis [p- (p-phenoxyphenoxy)phenyl]ether, and m-(m-phenoxyphenoxy) phenyl m-(o-phenoxyphenoxy)phenyl ether, and the his- (phenoxyphenoxyphenoxy)benzenes such as m-bis [m-(mphenoxyphenoxy phenoxy] benzene, p-bis [p- (m-phenoxyphenoxy)phenoxy]benzene and m-bis[m-(p-phenoxyphenoxy) phenoxy] benzene.

The preferred polyphenyl ethers are those having all their ether linkages in the meta-positions since the allmeta-linked ethers are particularly advantageous because of their wide liquid range and high thermal stability. However, mixtures of the polyphenyl ethers, either isomeric mixtures or mixtures of homologous ethers, can also advantageously be used in some applications, especially where particular properties such as lower solidification points are required. Mixtures of polyphenyl ethers in which the non-terminal phenylene rings are linked through oxygen atoms in the meta and para positions have been found to be particularly suitable to provide compositions with wide liquid ranges. Of the mixtures having only meta and para linkages, a preferred polyphenyl ether mixture of this invention is the mixture of bis(phenoxyphenoxy)benzenes wherein the non-terminal phenylene rings are linked through oxygen atoms in the meta and para position, and composed by weight of about 65% m-bis[m-phenoxyphenoxy]benzene, 30% m-[(mphenoxyphenoxy)(p-phenoxyphenoxy)Jbenzene and 5% m-bis-(p-phenoxyphenoxy)benzene. Such a mixture solidifies at below room temperature (that is, below about 70 F.) whereas the three components solidify individually at temperatures above normal room temperatures.

The aforesaid polyphenyl ethers can be obtained by known procedures such as, for example, the Ullman ether synthesis, which broadly relates to ether-forming reactions wherein alkali metal phenoxides such as sodium and potassium phenoxide are reacted with aromatic halides such as bromo-benzene in the presence of a copper catalyst such as metallic copper, copper hydroxides, or copper salts.

The high temperature, oxygenated carbonaceous base fluids employed in the compositions of this invention may also comprise a synthetic ester base fluid. These are fluids of lubricating viscosity and thermally stable to at least about 400 E, which are esters of alcohols containing at least 4 carbon atoms and which generally contain more than one ester group. They may be esters of polyhydric alcohols, of polybasic acids, or both.

The stated synthetic esters are generally aliphatic in nature, as distinguished from the essentially aromatic nature of the polyphenyl ethers, and their properties and response to additives have correspondingly been found to be usually of a different kind. Unexpectedly, however, the presently contemplated metallic additives have been found to provide significant improvement in the oxidation resistance of the stated ester type of base fluid also. Thus it appears that compositions comprising an adjuvant amount of a metal compound as defined above combined with a high temperature lubricant base fluid which, broadly, is an oxygenated carbonaceous base fluid are novel and valuable products with useful properties, and this invention extends to the provision of the stated general class of compositions.

Ester fluids with particularly advantageous low temperature viscosity properties, which flow readily at temperatures as low as 30 F., are provided by the diesters of dibasic acids. Ester lubricants of the dibasic acid ester type are illustrated by diesters of long chain dicarboxylic acids like azelaic acid with long-chain branched primary alcohols of the C to C range. The synthetic ester lubricants also frequently include the esters of long chain monobasic acids such as pelargonic acid with glycols such as polyethylene glycols. Complex esters are also formed by linking dibasic acid half esters through a glycol such as dipropylene glycol, a polyethylene glycol of 200 molecular weight, and so forth. Permutation and combination of these methods of forming polyester type lubricant fluids have been reported to be valuable and also, it is common practice to achieve desired properties in the ultimate base fluid by blending different polyester products. Simple esters providing suitable fluids can be exemplified, for example, by bis(2-methylbutyl)sebacate, bis( 1 methyl 4 ethyloctyl)sebacate, bis(2-ethylhexyl)- sebacate, dipropylene glycol dipelargonate, the diesters of acids such as sebacic, azelaic and adipic acid with complex C3C10 primary branched chain alcohols such as those produced by the 0x0 process, polyethylene glycol 200 bis(Z-ethylhexyl sebacate), diisoamyl adipate, 1,6-

hexamethylene glycol di(2-ethylhexanoate), bis(dimethylamyl)azelate and so forth.

Ester fluids with particularly good high temperature oxidation resistance are provided by neopentyl polyol esters. The alcohols from which these esters are derived have the carbon structure of neopentane, with a central carbon atom surrounded by 4 substituent carbon atoms. Included in the neopentyl polyols are neopentyl glycol, trimethylolethane, trimethylolpropane and pentaerythritol. Generally, the base fluids comprising neopentyl polyo1 esters are the esters with monocarboxylic acids. Such esters are generally more oxidatively and thermally stable than the dibasic acid esters. The useful esters of the neopentyl polyols include, for example, the esters of trimethylol propane, neopentyl glycol and pentaerythritol with normal, branched chain and mixed acids having chain lengths varying from C to C Thus, an illustrative series of esters are trimethylolpropane tri-npelargonate, trimethylolpropane tricaprate, trimethylolpropane tricaprylate, the trimethylolpropane triester of mixed octanoates, and the like.

For further description of still other ester fluids adapted for use as lubricant base stocks and useful in the provision of the blends of this invention, reference may be 5 made, for example, to the discussion in Gunderson et 211., Synthetic Lubricants (Reinhold, 1962).

The base fluid in the present compositions may c-onsist essentially of a polyphenyl ether base fluid alone, a synthetic ester base fluid alone, or a combination of the polyphenyl ether with a synthetic ester base fluid. The polyphenyl ethers are not generally miscible with other base fluids: they do not dissolve more than about 5% by weight mineral oil, for example. Attempts to blend silicones with the phenyl ether base fluids have shown that only a few of this class of fluids are miscible with the polyphenyl ethers, and then to a limited extent. However, it has been found that the polyphenyl ethers can be combined with other oxygenated carbonaceous base fluids to provide homogeneous fluids having advantageous properties.

A deficiency of the polyphenyl ether base fluids having exceptional thermal and oxidative stability, as exemplifled by the bis(phenoxyphenoxy)benzenes discussed above, is lack of fluidity at low temperatures. The fluid range of these materials is unusually Wide, encompassing the range from below 100 F. to above 800 F. However, the pour point of certain of these particularly stable fluids is above F., whereas for lubricant use, for example, ability to flow down to temperature climate winter temperatures such as 0 F. is desirable. It has been found that compositions comprising combinations of ester basefluids and the polyphenyl ethers can be provided which have the desired fluidity at low temperatures.

The lubricant fluids which have been found to blend with the phenyl ethers of good thermal and oxidative stability include various esters. It is particularly desirable to provide blends having thermal and oxidative stability at least approaching the stability of the polyphenyl ethers. In this connection, especially valuable base fluids have been found to be provided by combinations of a polyphenyl ether with a neopentyl alcohol ester. These compositions possess both fluidity at low temperature and stability at elevated temperatures.

The preferred polyphenyl ethers for use in this connection are the bis(phenoxyphenoxy)benzenes, of the composition C H O(C H O-) -C H where each C H is a phenyl and each C H is a phenylene radical. Those with the ether linkages between benzene rings in meta positions, partly or wholly, are especially preferred. The stated neopentyl esters are esters of neopentyl alcohols such as pentaery-thritol, trimethylolethane, trimethylolpropane and neopentyl glycol with straight chain, branched chain and mixed C -C acids such as n-heptanoic and neoheptanoic acid.

Compositions of the stated valuable nature are provided by combining 2575 weight percent of the ester base fluids with 75-25 weight percent of the polyphenyl ethers.

Referring to the additives combined with the abovedescribed base fluids in accordance with this invention, these are bis(o-formimidoylphenolato) metal (II) compounds wherein the metal radical attached to the oxy function of the phenolato radical is a divalent, tetracoordinating metal, the nitrogen atom of the formimidoyl radical has a substituent selected from aliphatic saturated hydrocarbon and aromatic substituents, and the benzene ring of the phenolato radical has \from O to 2 nitro substituents.

The metal in the stated compounds may be selected from any of a wide variety of the available salt-forming elements having a primary valence of two and tetracoordinating in at least one of the oxidation states of the metal. As will be appreciated from the above-stated formula, the metals form coordinative chelate bonds to the nitrogen atom of the formimidoyl groups in the compounds, in addition to the primary valence bonds they form with the oxygen atoms attached to the phenolato radicals. The chelating, divalent metals of these salts may be metals of Group I, such as copper, of Group II, such as zinc, transition metals such as cobalt (II) and 6 nickel (II), or indeed, Pb, V, Cr, Mn, Pt, Pd, Fe, and other metals able to assume the divalent, tetracoordinating state. Transition metals are preferred, and Ni and Co especially preferred.

The N substituent in the [formimidoyl groups of the presently employed additives may be a hydrocarbon radical or may be a radical including hetero atoms which is aromatic in character, said substituent being free of aliphatic (olefinic or acetylenic) unsaturation. By a radical which is aromatic in character is meant a radical including conjugated unsaturation of the configuration found in the benzene ring, including heterocyclic tertiary amines in which the N atom is part of the conjugated unsaturated ring structure, such as pyridine, and ethers wherein the oxygen ether atom joins aromatic rings, such as phenoxyphenyl, as well as aromatic hydrocarbon radicals, with or without aliphatic substituents, such as phenyl and tolyl. The N substituents on the two formimidoyl groups of the present bis(o-formimidoylphenolato) metal (II) compounds may be the same or different, and may be a monovalent radical or a divalent radical joining the two N atoms in the compound. The N substituent may include from 1 :to 18 carbon atoms, and most preferably, from 1 to 12.

The phenolate nucleus in the stated compounds may be substituted solely by H atoms in the four positions open on the nucleus, or one or two of the ring substituents may be a nitro group.

Exemplary of the additives employed in compositions of this invention, accordingly, are bis(o-formimidoylphenolato) metal (II) compounds having aliphatic N substituents such as bis [0- (N-butylformimidoyl) phenolato nickel,

bis [0- N-butylformimidoyl) phenolato] cobalt,

bis [0- (N-butylformimidoyl) phenolato] zinc,

bis [0- (N-isopropylformimidoyl) phenolato] nickel,

bis [0- (N-isoamylformimidoyl) phenolato] cobalt,

bis [o- (N-2-ethylhexylformimidoyl) phenolato] nickel,

bis [0- (N-2-ethylhexylformimidoyl) phenolato] cob alt,

bis [0- (N- 1 1-dimethyloctylformimidoyl) phenolato] cobalt,

bis [2- (N-butylformimidoyl) -5-nitrophenolato] nickel,

bis [2- (N-butylformimidoyl) -5-nitrophenolato] cobalt,

bis [0- (N-Z-ethylhexylformimidoyl) -5 -nitrophenolato] nickel,

bis {0- N-cyclohexylformimidoyl) -5-nitrophenolato] cobalt,

2,2- [ethylenebis (nitrilomethylidyne) diphenolato nickel,

2,2- [ethylenebis (nitrilomethylidyne) ]bis [5-nitr0- phenolato] nickel,

2,2'- [ethylenebis (nitrilomethylidyne) ]bis [S-nitrophenolato] cobalt,

2,2'- [trimethylenebis (nitrilomethylidyne) ]bis [S-nitrophenolato] copper, and so forth.

The N-aromatic-hydrocarbon-substituted additives 1n the scope of this invention are exemplified by bis [0- (N-phenylformimidoyl) phenolato] nickel,

bis [0- (N-phenylfonnimidoyl) phenolato] cobalt,

bis [0- N-phenylformimidoyl) phenolato] zinc,

bis [0- (N-phenylformimidoyl) phenolato] copper,

bis [0- (N-tolylformimidoyl) phenolato] nickel,

bis [0- (N-benzylformimidoyl) phenolato] cobalt,

bis [0- (N-naphthylformimidoyl) phenolato] nickel,

bis [0- (N-biphenylylformimidoyl) phenolato] nickel,

bis [0- (N- a-cumylformimidoyl phenolato] nickel,

bis [0- (N- [p-t-butylphenyl] Lformimidoyl) phenolato] nickel,

bis [2- (N-phenylformimidoyl) -5-nitrophenolato] nickel,

bis [2- (N-phenylformimidoyl) -5-nitrophenolato] cobalt,

bis 2- (N-phenylformimidoyl) -5-nitrophenolato 1 iron,

bis [2- (N-phenylformimidoyl) -5-nitrophenolato] cadmium,

bis [2- (N-phenylformimidoyl --nitrophenolato] tin,

bis 2- (N-phenylformimidoyl) -3-nitrophenolato] nickel,

bis [2- (N-phenylformimidoyl) -3 ,S-dinitrophenolato] nickel,

bis [2- (N-naphthylformimidoyl) -5-nitrophenolato] nickel,

bis [2- N-biphenylylformimidoyl) -5-nitrophenolato] cobalt,

bis [2- (N- a-cumylformimidoyl) -5-nitrophenolato] nickel,

2,2'- [o-phenylenebis (nitrilomethylidyne) ]diphenolato nickel,

2,2'- [o-phenylenebis (nitrilomethylidyne) diphenolato cobalt,

2,2'- [o-phenylenebis (nitrilomethylidyne) ]bis S-nitrophenolato) nickel,

2,2'- 1,2-diphenylethylenebis(nitrilomethylidyne) ]bis (S-nitrophenolato nickel, and so forth.

Illustrative of the additives contemplated herein with N substituents including hetero atoms and having an aromatic character are bis[o-N-p-phenoxyphenylformimidoyl)phenolato]nickel, bis[o (N phenoxyphenylformimidoyl)phenolato]cobalt, bis[o (N-2 pyridylformimidoyl)phenolato]nickel, bis[o N-Z-quinolinylformimidoyl phenolato] cobalt, bis [o- N-4-a-picolinylformimidoyl)phenolato]nickel, bis[o-(N-2-pyrazinylformimidoyl) phenolato]nickel, bis[2-(N-Z-pyridylformimidoyl)-5 nitrophenolato] nickel, bis [2- (N-2-pyridylformimidoyl -5- nitrophenolato] cobalt, bis [2- N-Z-pyridylformimidoyl) S-nitrophenolato] copper, bis 2- N-p-phenoxyphenylformimidoyl)-5-nitr0phen0lat0]nickel, and so forth.

The stated additives may be employed in the present compositions alone or in combination.

Bis [2- (N-phenylformimidoyl) -5-nitrophenolato] nickel, which is a particularly eifective additive, has been observed not to be completely soluble in a bis(phenoxyphenoxy)benzene fluid in any proportion, even after prolonged heating. This can be explained by postulating the existence of a diamagnetic monomer/paramagnetic dimer equilibrium, with diamagnetism favoring solubility. It has been found in this connection that addition of bis [o-(N-phenylformimidoyl) phenolato] nickel, which is soluble in all proportions in the bis(phenoxyphenoxy) benzene fluid, solubilizes the nitro compound. Mixtures of his [2- (N-phenylformimidoyl -5-nitrophenolato] nickel and bis[o-(N-phenylformimidoyl)phenolato]nickel accordingly form an especially preferred additive in the presently provided compositions.

The metal compound is combined with the base fluid to the extent of, generally, between about 0.01% and by weight of the fluid. Particular effective amounts depend on the nature of the individual additive and of the base fluid. In some cases, the ability of the present agents with respect to oxidation stability improvement increases as the concentration is increased, which is contrary to the concentration effects obtained with other antioxidant additives such as organotin compounds in the presently employed base fluids.

It will be appreciated that the compositions of this invention, in addition to the base fluid and the antioxidant metal compound additive, may additionally include any of a wide variety of further additives. For example, the base fluids may be combined with lubricity improvers effective to increase load-carrying ability, decrease wear, or both, with viscosity index improvers such as polymethacrylate alkyl esters, with detersives and dispersants, and so forth.

The presently employed antioxidant additives may also advantageously be employed in conjunction with other antioxidant additives. Particularly good oxidation resistance can be attained by combining the presently employed bis(o-formimidoylphenolato) metal (11) compounds with organic antioxidants such as aryl amines, with organometallic additives such as organotin com- 8 pounds, and with other metal chelates such as alkanedionato metal compounds, for example.

The invention is illustrated but not limited by the following examples, in which the tests employed to determine the reported adjuvant effects of the additive compounds when employed with the polyphenyl ether lubricant base fluid are conducted as follows:

For determination of the antioxidant effect of the present additive compounds, air is bubbled through heated samples of the base fluids and base fluids plus additives. The percent change in F.) viscosity from before to after oxidation is an index of anti-oxidant activity. The conditions employed are temperatures of 500 or 600 F. and a flow rate of 1 liter (or, in advanced testing, 20 liters) of air per hour. Samples are run in the presence and absence of metal wires (silver, copper, aluminum, stainless steel) as a check on the effect of such metals on the oxidation rate.

The antiwear and extreme pressure lubrication characteristics of the lubricant compositions are evaluated by means of the well known Shell 4-Ball Extreme Pressure Tester and the Shell 4-Ball Wear Machine, as described, for example, in the Lubrication Engineers Manual (US. Steel Corp., 1960). These testers include 4 balls of stainless steel arranged in the form of an equilateral tetrahedron. The three lower balls are held immovably clamped in a holder to form a cradle in which the fourth upper ball is caused to rotate at 12001800 r.p.m. about a vertical axis in contact with the three lower stationary balls. The contacting surfaces of the balls are immersed in the test fluid which is held in a cup surrounding the assembly. A modified cup and heater assembly is used to evaluate lubricants at elevated temperature and provisions are made to permit high temperature testing under an inert atmosphere: see the The Study of Lubrication Using the 4-Ball Type Machine by R. G. Larsen, Lubrication Engineering, 1, 35-43, 59 (August 1945).

For determination of the extreme pressure properties in the 4-ball EP tester, the upper ball is rotated while the load is gradually increased by increments of 10 kg. until the balls are welded together in a l-minute test period.

For measurement of Wear in the Wear Machine, the upper ball is rotated under a load of 40 kg. for one hour at 400 F.

Example 1 This example illustrated the effect of individual bis- (o-formimidoylphenolato) metal compound additives on a polyphenyl ether base stock.

Compositions as provided by this invention are prepared by combining a polyphenyl ether base stock of the following composition, by weight:

65 m-bis m-phenoxyphenoxy) benzene 30% m [(m phenoxyphenoxy) (p phenoxyphenoxy)] benzene 5 m-bis (p-phenoxyphenoxy) benzene with bis(o-formimidoylphenolato) metal (II) compounds as follows:

Bis [o- (N-phenylformimidoyl phenolato] nickel (Ni) Bis[2 (N phenylformimidoyl)-5-nitrophenolato] cobalt Bis[2 (N phenylformimidoyl)-5-nitrophenolato)nickel (Ni-2) Results of the 24 hour preliminary oxidation test run at 600 F., at a one liter air per hour rate, using Cu, Al, Ag and Fe wires, are shown in the following table. In the table, the compositions including the additives are identified by the additive designations given above, and the concentrations of the additives are shown in grams (g.) per 100 g. of base stock.

In this test, the base stock exhibits a viscosity increase of about 40% in the presence of the metal wires and about 60% in their absence. 7 a

[100 F. viscosity, cs.]

After Percent After Percent Additive Cone. Initial test with change tcst no change wires wires Example 2 This example further illustrates the antioxidant effect of the additives on a polyphenyl ether base stock.

The base stock used to obtain the compositions and results stated below has the composition stated in EX- ample 1, and has been purified by distillation from an admixture of a sodium-lead alloy with the base fluid of Example 1.

Compositions submitted to test as described below are prepared by combining the stated base fluid with the following salts, in concentrations (g./ 100 g. base stock) as stated:

g./100 g. (1) Bis[2 (N 2 pyridylformimidoyl) 5 nitrophenolato1copper' 1.0 (2) Bis[2 (N phenylformirnidoyl) 5 nitrophenolato1zinc 2.0 (3) Bis[2 (N phenylformimidoyl) 5 nitrophenolatoJnickel 2.0 (4) Bis[2 (N phenoxyphenylformimidoyl) 5- nitrophenolato]nickel 1.0 (5) Bis[2 (N phenoxyphenylformimidoyl) 5- nitrophenolato1cobalt 2.0

The viscosity increase produced by a 1 liter per hour air flow at 600 F. for periods of 24, 48 and 72 hours, in the presence and absence of metal wires, is measured for these compositions. The base stock exhibits a viscosity increase of about 20% in 24 hours in the presence of wires, and in their absence, about 40% in 24 hours and about 100% in 48 hours.

24 HOURS [100 F. viscosity, cs.]

This example illustrates the antioxidant effect of combinations of diiferent (0-formimidoylphenolato) compounds on a polyphenyl ether base fluid.

The base fluid employed in preparing the compositions of this example has the composition described in Example 2, which increases in viscosity about 20% in the presence of the metal Wires and about 40% in their absence, in the 24 hour, 1 liter per hour air flow, 600 F. preliminary oxidation test.

To provide compositions consisting of the stated base fluid and fully solubilized bis[Z-(N-phenylformimidoyl)- S-nitrophenolato1nickel, the latter salt is added to the base fluid, and the mixture is filtered at a temperature of F. Cooling to room temperature (about 70 F.) produces a cloudy fluid, to which bis[o-(N-phenylformimidoyl)phenolato1nickel is added. The product is a clear fluid at room temperature.

Compositions are prepared by combining the stated base fluid with varying amounts of both bis[2 (N- phenylformimidoyl) 5 nitrophenolato1nicke1 and bis[o (N phenylformimidoyl)phenolato1nickel, and these are submitted to the 600 F. 24 hour oxidation test. Results are shown in the following table, in which the concentration of each nickel salt is shown in g./ 100 g. base fluid, with the concentration of the nitro-substituted compound given first, and the unsubstituted, second:

[100 F. viscosity, cs.]

Additive Cone. Initial After test Percent After test Percent with wires change no wires change 2.0/2.0 513 521 1. 7 517 0.9 2.0/2.0 430 477 ll 2.0/2. 408 432 5. 8 425 4. 3 2.0/l. 457 473 3. 5 457 0. 0 2.0/1.0. 394 421 7. l 1.0/1.0. 418 428 2. 5 425 1.6 1.0/1.0--. 403 435 7.9 1.0/0.5. 401 400 0.0 1.0/0.5. 401 410 2. 4 405 1. 1 2.0/0.75 404 423 4. 6 425 5. 1 1.5/0.75 410 413 0.7

Example 4 This example further illustrates the beneficial effects of additive combinations in accordance with this invention, and illustrates compositions according to the invention including (N-alkylformimidoyl)phenolato salts.

The base fluid described in Example 2 is combined with combinations of bis[2 (N butylformimidoyl)- 5 nitrophenolato1nickel and bis[o (N phenylformirnidoyl)phenolato]nickel, in concentrations (g./ 100 g. base fluid) as shown respectively first and second in the following table. These compositions are subjected to the 600 F., 24 hour, 1 liter air per hour oxidation test, in which the base fluid alone has a viscosity increase of about 20% in the presence of Wires and about 40% in their absence, with the following results:

[100 F. viscosity, cs.]

This example illustrates compositions in accordance with the invention using combinations of salts having different cations.

Compositions are prepared by adding combinations of bis[2 (N phenylformimidoyl) 5 nitrophenolato] nickel and bis[2 (N phenylformimidoyl) 5 nitrophenolatolcobalt to the polyphenyl ether base fluid described in Example 2, which alone shows a 24 hour 600 F. viscosity increase of about 20% in the presence and about 40%. in the absence of Wires in the 1 liter air per hour oxidation test. The compositions including the nickel and cobalt salts are subjected to a one liter air flow per hour at 600 F. in preliminary oxidation tests for 24 and 48 hours. The following table showing the results states the concentration of the cobalt and nickel salt additives respectively, in g./ 100 g. base fluid.

This example illustrates compositions according to the invention containing organotin compounds and containing ternary additive combinations.

The polyphenyl ether base fluid of Example 2 is combined with additive combinations as shown below.

and 600 F., 24 hour preliminary oxidation tests are run on the resulting compositions with the following results:

[100 F. viscosity, cs.]

Composition Initial After test Percent After test Percent with wires change no wires change Example 7 This example further illustrates antioxidant effects of the additive in a composition of this invention.

Portions of a polyphenyl ether base fluid which is a bis(phenoxyphenoxy)benzene mixture of the composition stated in Example 1 are combined with bis[2 (N phenylformimidoyl) 5 nitrophenolato1nickel in a concentration of 2.0 g./10O g. base stock, and with bis(pphenoxyphenyl)diphenyltin, in a concentration of 1.0 g./100 g. base stock, respectively. The tin compound is an effective antioxidant for this polyphenyl ether, increasing the useful life as an engine lubricant from 10 hours for the uninhibited base stock to 80 hours for the stock containing this concentration of the tin compound.

Using the Dornte oxidation apparatus, uptake of oxygen by the two stated compositions is measured. It requires 21 hours for the composition containing the nickel additive to absorb as much oxygen as the fluid containing the tin additive takes up in 13 hours, at 600 F.

Example 8 This example illustrates the eifect of the additives in the present compositions on lubricity properties of the polyphenyl ether base stocks.

Compositions are prepared by combining the polyphenyl ether base fluid described in Example 2 with additives as follows.

Compn. additive: Conc., g./100 g.

Bis[o (N-phenylformimidoyl)phenolato]nickel 2.0

and subjected to the 600 F., 24 hour, 1 liter air per hour oxidation test described above. Then the lubricity properties of the oxidized compositions are measured by the Shell 4-Ball Extreme Pressure and Wear tests described above. Results are shown in the following table, which includes for comparison the corresponding values for the uninhibited base fluid (unoxidized).

Composition Weld point, kg. Wear scar diameter,

mm, at 40 Example 9 This example illustrates compositions including the present additives and base stocks consisting of blends at polyphenyl ether base fluid and a polyester base A blended base stock having a pour point below 0 F. is prepared by combining a polyphenyl ether base stock consisting of the mixture of bis(phenoxyphenoxy)benzenes described in the above examples and trimethylolpropane tri-enanthate, in the ratio of 55% by weight of the polyphenyl ether to 45% of the ester base stock (TMP Blend 1). This blend has a 100 F. viscosity of about 50 0s, which is approximately doubled by exposure to an air flow of one liter per hour for 24 hours at 500 F. in the presence of Al, Cu, Ag and Fe wires.

A composition prepared by combining this blend with bis[2 (N 2 ethylhexylformimidoyl)-5-nitrophenolato] nickel, in a ratio of 1.0 g. of the nicket salt per 100 g. of the blend, undergoes only about a 50% increase in viscosity under the same conditions.

A fluid composition is prepared by introducing the same concentration of the same additive into a blend (TMP Blend 2) with the above-stated viscosity and oxidation characteristics, which is 55% by weight mixed (phenoxyphenoxy)benzenes of the same composition as before, and 45%, a trimethylolpropane triester with mixed alkane carboxylic acids of about C chain length. This composition exhibits a 100 F. viscosity increase of about 40% in 23 hours under the same conditions.

Introducing 1.0 g./1OO g. base stock of bis[o-(N- phenylformimidoyl)phenolato1nickel as antioxidant additive in the latter blend, the initial viscosity is 49.2, and this increases by only 25% in the 24 hour, 1 liter air flow, 500 F. oxidation test. With this composition, no evaporation loss takes place in the test, whereas the blended base stock alone exhibits an average evaporation loss of 2.5% of its weight under the same conditions.

Example 10 This example further illustrates compositions according to this invention in which the base stock is an ether/ester blend.

Additive packages are prepared in which o-formimidoylphenolato metal compounds are combined with amine and tin compounds as follows.

No. 1 additive: Parts by weight Triphenylamine 5.0 Bis o- (N-phenylformimidoyl) phenolato] nickel 1.0 Bis[Z-(N-phenylformimidoyl)-5-nitrophenolato] nickel 1.0

No. 2 additive:

Bis(p-phenoxyphenyl)diphenyltin 5.0 Bis [o- (N-phenylformimidoyl) phenolato] nickel 1.0 Bis [2- (N-phenylformimidoyl -5-nitrophenolato] nickel 1.0

These additive packages are combined, in a proportion of 7 g. total of additives per 100 g. of base fluid, with the trimethylol propane ester blends with polyphenyl ethers described in the preceding example, identified respectively as TMP Blend 1 and TMP Blend 2, and with blends of the previously described mixed bis(phenoxyphenoxy)benzenes base fluid with pentaerythritol tetracaproate, in etherzester weight proportions of 50:50 (PE Blend 1) and 45:55 (PE Blend 2), respectively.

The results obtained in the oxidation test at 1 liter per hour air flow, 24 hours, 500 F., in the presence of Al, Cu, Ag and Fe wires, for the blends and the blends plus the additive packages are as follows (values for the TMP blends, averages of replicate samples):

[100 F. viscosity, cs.]

When the above-described oxidation test is conducted using an air flow rate of 20 liters per hour, with conditions otherwise the same (500 F., 24 hours, presence of metal wires), the TMP blends increase in viscosity from an initial value of about 50 cs. to an after-test viscosity which is above 500 es. With the compositions comprising the additive packages described above, this oxidation is substantially reduced, as shown in the following table:

[100 F. viscosity, cs.]

TMP blend No. Additive N0. Initial Alter test Example 11 This example illustrates compositions according to the invention including still another additive combination.

The blend described in the preceding examples as TMP Blend No. 1 is combined with (A) 1.0 g./l g. of base stock of tris(2,4-pentanedionato)cobalt and with (B) 1.0 g./O g. base stock each of tris(2,4-pentanedionato)cobalt and bis[o (N phenylformimidoyl)phenolato]nickel. This base stock blend, as above stated, increases in viscosity from about an initial value of 50 cs. to about 100 cs. after the test at a 1 liter per hour air flow rate. The oxidized stock is dark in color, but clear and free of solids. Upon subjecting composition (A), consisting of this blend stock and the cobalt chelate, to the same test, the initial viscosity is 52 cs., and after oxidation, it is 56 cs., an increase of only 8%. However, the oxidized fluid contains fine solids, which is not an uncommon result of the oxidation test, particularly for compositions containing metallic additives.

Composition (B), consisting of the blend plus both the Co and the Ni additives, changes from an initial viscosity of 54 to a final value of 57 cs., which is an increase of only 6%, with an evaporation loss of 5.0%, while the oxidized composition remains clear.

Example 12 This example further illustrates compositions according to the invention, using a difierent base fluid.

A blend is prepared consisting of 55%, by weight, of the bis(phenoxyphenoxy)benzenes mixtures described in the preceding examples, and 45% of bis(1-methylcyclohexyl) sebacate. The F. viscosity of this blend is cs. After exposure to the 500 F., 24 hour, 1 liter air flow preliminary oxidation test in the presence of metal wires, the viscosity has increased to cs., an increase of 76%. When the blend is combined with 1.0 g./l00 g. base fluid each of bis[o-(N-phenylformirnidoyl)phenolatoJnickel and bis[2 (N phenylformimidoyl) S-nitrophenolato1nickel, the viscosity before test is 118 cs. and after exposure to the same oxidizing conditions as the blend alone, the viscosity is 129 cs., which is an increase of less than 10% Example 13 This example illustrates compositions including additives according to the invention and ester fluids.

A concentration of 2.0 g./100 g. base fluid of bis[2- (N-phenylformimidoyl)-5-nitrophenolato]cobalt is combined with pentaerythritol tetracaproate and with bis(1- methylcyclohexyl) sebacate, and the 500 F. oxidation stability of these compositions is measured, In each case, the oxidation stability of the ester base fluid is increased.

While the invention has bee-n described with particular reference to various specific preferred embodiments thereof, it is to be appreciated that the modifications and variations may be made without departing from the scope of the invention, which is limited only as defined in the appended claims.

What is claimed is:

1. A functional fluid composition comprising a polyphenyl ether base fluid and an antioxidant amount of at least one bis(o-formimidoylphenolato) compound with a metal having a primary valence of 2 and tetra-coordinating in at least one of its oxidation states of the formula where M is a divalent, tetracoordinating metal cation, 11 and m are integers of from 0 to 2, and R and R are organic substituents selected from the class consisting of aliphatic saturated hydrocarbon and aromatic radicals, containing from 1 to 18 carbon atoms.

2. The composition of claim 1 wherein said metal is a transition metal.

3. The composition of claim '1 wherein said metal is nickel.

4. The composition of claim 1 wherein at least part of the bis(o-formimidoylphenolato) compound with a metal is a bis[2 (N substituted-formimidoyl)nitrophenolato]rnetal compound.

5. The composition of claim 4 wherein the bis(o formimidoylphenolato) compound with a metal in said fluid composition is a mixture of a bis[-o(N+arylf-ormimidoyl)nitrophenolato]nickel compound and a bis[o-(N- substituted-formimidoyl)phenolato]nickel compound in an amount suflicient to solubilize said nitrophenolato compound.

6. The composition of claim 1 in which the base fluid consists essentially of a polyphenyl ether.

7. The composition of claim 1 in which the base fluid consists essentially of a blend of an ester and a polyphenyl ether base fluid.

8. The composition of claim 1 in which said composition comprises an additional oxidant other than said bi*s[o-(N substituted-formimidoyl)phenolato]metal compound.

9. A functional fluid composition consisting essentially of a polyphenyl ether base fluid consisting of from 3 to 7 benzene rings joined in a chain by oxygen atoms as ether linkages between each ring and an antioxidant amount of at least one bis[o-(N-substituted-formimidoyl) phenolato]metal compound of the formula where M is a divalent, tetracoordinating metal cation, 11 and m are integers of from to 2, and R and R are organic substituents selected from the class consisting of aliphatic saturated hydrocarbon and aromatic radicals, containing from 1 to 18 carbon atoms.

10. The composition of claim 9 in which at least part of said bis[o (N substituted formimidoyl)phcnolato] metal compound is bis[o-(N-phenylformimidoyl)phenolato]nickel.

11. The composition of claim 9 in which the bis[o- (N substituted vformimidoyl)pher1olato]metal compound in said fluid composition is a mixture of bis[o-(N-phenylfiormimidoyl)phenolato]nickel and bis[2-(Nphenylformimidoyl)-5-nitrophenolato1nickel.

12. The composition of claim 9 in which the said polyphenyl ether base fluid consists of a mixture bis (phenoxyphenoxy)benzenes.

13. A functional fluid composition consisting essentially of a base fluid comprising a mixture of his (phenoxyphenoxy)benzenes and an amount of bisIZ-(N-p'henylformlimidoyl) 5 nitrophenolato1nickel eifective to increase the oxidation resistance of said bis(phenoxyphenoxy) benzenes mixture.

14. A functional fluid composition consisting essentially of a base fluid comprising a mixture of bis(phenoxyphenoxy)benzenes, an amount of bis[2-(N-phenylformimidoyl)-5-nitrophenolato]nickel effective to increase the oxidation resistance of said bis(phenoxyphenoxy)benzenes mixture, and an amount of bis[o-(N-phenylfiormimid-oyl)phen-olato]nickel suflicient to solubilize the said bis [2- (N-phenylformimidoyl -5-nitrophenolato] nickel in said bis(phenoxyphenoxy)benzenes mixture,

15. The composition of claim 13 in which the base fluid is a blend of said bis(phen oxyphenoxy)benzenes mixture and a neopentyl glycol ester base fluid.

16. A functional fluid composition in which the base fluid is a mixture of a polyphenyl ether consisting of from 3 to 7 benzene rings joined in a chain by oxygen atoms as ether linkages between each ring, and a neopentyl glycol ester with a monobasic saturated alkanoic acid of from 5 to 10 carbon atoms, and combined with said base fluid, an antioxidant amount of at least one bis [0 (N substituted formimidoyDphenolato]metal compound of the formula HO=NR1 Rr-N=CH where M is a divalent, tetracoordinating metal cation, 11 and m are integers of from 0 to 2, and R and R are organic substituents selected from the class consisting of aliphatic saturated hydrocarbon and aromatic radicals, containing from 1 to 18 carbon atoms.

17. The functional fluid composition of claim 16 in which the said polyphenyl ether consists of mixed bis (phenoxyphenoxy)benzenes.

18. The composition of claim 16, said composition comprising an additional antioxidant other than the said his 0- (N-substituted-formimidoyl phenolato] metal compound.

References Cited by the Examiner UNITED STATES PATENTS 2,615,860 10/1952 Burgess 260429 FOREIGN PATENTS 851,651 10/1960 Great Britain.

OTHER REFERENCES Calvin et al.: Journal of the American Chemical Society, vol. 68 (1946), p. 2267. 

1. A FUNCTIONAL FLUID COMPOSITION COMPRISING A POLYPHENYL ETHER BASE FLUID AND AN ANTIOXIDANT AMOUNT OF AT LEAST ONE BIS(O-FORMIMIDOYLPHENOLATO) COMPOUND WITH A METAL HAVING A PRIMARY VALENCE OF 2 AND TETRA-COORDINATING IN AT LEAST ONE OF ITS OXIDATION STATES OF THE FORMULA 